Private branch exchanges (PBXs) and other call switching devices receive incoming telephone calls to an establishment and distribute the calls to available agents at the establishment. However, sophisticated call distribution involving facilities such as multiple caller queues for servicing multiple categories of callers is only available at the cost of acquiring large amounts of expensive and specialized equipment. For example, automatic call distributors can handle large numbers of incoming and outgoing calls simultaneously, and they can manage calls by holding them in queues until an agent is available to receive the call. These systems are expensive to install and expensive to modify.
Many of the users of call switching systems use them to distribute calls to banks of agents who respond to callers' requests with the help of application programs developed at the user's establishment. These application programs typically operate on host computers and are used to organize and process large databases of information related to the business, customers and/or market of the user. The functions provided by these application programs include responding to agent inquiries to send data in a particular format or responding to requests for information on particular subjects or items. Users also can use application programs to tailor-make the agent's interface with the application program for displaying the information necessary for the agent to handle the calls he or she receives. Users also use the application programs for performing statistical and other analyses on the data that are uniquely suited for the user's business.
In the past, it was difficult to integrate a telephone call with the data that related to the purpose of the call or the identity or business of the caller. Agents using application programs were forced to request information from a host computer running the application program only after receiving the telephone call from the PBX and obtaining key information from the caller. This procedure was time-consuming, and prone to errors. Furthermore, if the agent transferred the call, the data obtained from the host computer could not be transferred with the call and was lost.
Recently, one proposed solution to the problem of voice/data integration has been the use of Request and Status Links (RSLs) linking an automatic call distributor (ACD) or a PBX and the host computer. The RSL includes a piece of hardware providing a physical channel between, for example, an ACD and the host computer and software providing one interface between the host computer and the RSL and another interface between the ACD and the RSL. While allowing the host computer to transfer data to agents at the same time as the ACD transfers the call, this approach suffers from several constraints. For example, in order to protect the secrecy of the ACD's software, and leverage the investment in ACD software, RSLs impose call handling protocols on RSL requests that impose constraints on the host computer's access to the RSL's services. A considerable amount of customization to the host's operating system, host hardware and telephone equipment is required by users of RSLs. Frequently an RSL installation requires special hardware that is often incompatible with existing equipment. This incompatibility sometimes necessitates extensive and costly upgrades of the equipment, including the ACD itself.
An RSL installation also requires extensive re-configuration of the user's application programs running on the host computer to allow for coordination of call and data transfer. This reconfiguration can be extremely expensive and time consuming and must be done very carefully, because the application programs very often constitute the user's most valuable asset. Furthermore, each RSL only works on particular models of automatic call distributors, requires digital telecommunication technology, and must adhere to rigid, often proprietary, protocols. Furthermore, purchasers of RSLs often cannot add additional features without a great deal of effort, specialized knowledge and extensive testing.
A proposal for more flexible RSL-type systems is to use an international standard such as Integrated Services Digital Network (ISDN). ISDN allows for moving data and voice over the same path through the telephone lines. If an establishment uses ISDN compatible equipment, it can add other equipment, including additional ACDs and stations, without significantly changing its original system, provided the added equipment also conforms to ISDN. However, ISDN suffers from many deficiencies, including requiring a slow transmission speed of 144 kb/second (maximum). Furthermore, most existing systems are incompatible with ISDN. Consequently, ISDN does not avoid the extensive upgrade costs associated with RSLs in general.